Materialized views: fix three error messages
Materialized views: fix three error messages

Three error messages were supposed to include a column name, but a "{}"
was missing in the format so the given column name didn't actually appear
in the error message. So this patch adds the missing {}'s.

Fixes #4183.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>
Message-Id: <20190203112100.13031-1-625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

avikivity/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla